Alternating-current electromagnet



G. E. PALMER.

ALTERNATING CURRENT ELECTROMAGNET.

APPLICATION FlLE DEC.10,1918.

Patented Jun 15, 1920.

CL /7 2f UNITED STATES PATENT OFFICE. f

GRANVILLE E. PALMER, 0F BOSTON, MASSACHUSETTS, ASSIGNOR TO THE PALMERELECTRIC & MANUFACTURING COMPANY, OF BOSTON, MASSACHUSETTS, A COR-PORATION 0F MAINE.

ALTERNATING-CURRENT ELECTROMAGNET.

Specification of Letters Patent. Patented June 15, 1920.

Application flled December 10, 1918. Serial No. 266,132.

To all 'whom z't may concern:

Be it known that I, GRANVILLE E. PALMER, a citizen of the United States,residing at Boston, in the county of Suffolk and State of Massachusetts,have invented new and useful Improvements in Alternating-CurrentElectromagnets, of which the tially in section.

Considered as an entirety, the magnet comprises two parallel solenoids10, 11, arranged in series ina single-phase alternating current circuit.As illustrated, thesesolenoids are secured by brackets 12 and 13 to asuitable upright base or support 14. Coperating with the solenoids orcoils 10, 11, are two plungers 15, 16, respectively,

which are'of course parallel and which project upwardly from a cross bar17, secured thereto or integral therewith, into the spools of saidsolenoids. The plungers 15, 16, and

cross bar 17 form a U-shaped member a.y

When a single-phase alternating circuit of suflicient voltage issupplied to the coils 10, 11, the U-shaped member is raised, asnaturally would be expected, to approximately lthe position shown inFig. 3. In conjunction with the member a, I provide an oppositelyarranged supplemental U shaped member b, which comprises a cross bar 19and parallel plungers 20, the latter extending downwardly into thespools 21 of the coils and being provided with fiat end por tions 22 tomake contact with the ends of' the plnngers 15, 16, when the' latter arein elevated poeitioi'il Under normal condin tions, when the solenoidsare denergized, the upper member rests loosely upon a support affordedby the upper portion of the4 solenoids, with the plungers 20 extendingdownwardly ytoward the middle portion of said solenoids, and the lowermember is at the lower limit of its movement with its plungers separatedfrom those of the upper member, all as shown in Fig. 1. When asingle-phase alternating currentr of not less than predeterminedpotential is supplied to the solenoids, the lower armature member isdrawn upwardly and the magnetic force tends to draw the upper armaturemember down into the solenoids, which is, of course.` resisted by thestationary portion of the solenoid upon which the upper member rests.The magnetic mass of the lower member is so proportioned to that of theupper member that under the condition recited the latter is lifted fromits support by the lower member, and the two members, with their ends incontact, float inthe magnetic field, a magnetic circuit being completedthrough the armature.

In order that the upper member 18 `may not be displaced mechanically, Iemploy any suitable guide or holder therefor. One, comprising a Uishapedstrap 23, may be employed, which bridges the cross bar 19 but which isof such dimensions as not to interfere with the free movement of theupper member and not to make mechanical contact therewith when thelatter is float ing. f

I have observed (and it is a characteristic of the magnet which I havedescribed) that,

when the coils are excited by a current of the desired given potentialand the armature is floating in the magnetic field, no hum or chatteringcan be detected. If the potential is gradually lowered, the armaor humis heard. The parts remainl in this position during the continuedgradual lowering of potential inthe exciting circuit until a certainminimum voltage is reached, whereupon they lower solenoid; is suddenlyreleased and dropsI Thisv is doubtless due ture drops until the uppermember rests f upon its support, whereupon a chattering to the fact thatthe U-shaped alternatelydisposed members are mutually attractedmagnetically, and remain lin contact until the loss of potential in theexciting circuit is suflicient to enable the weight or mass of the lowermember to overcome the mutual magnetic attraction and cause its suddenrelease.

Considered in one aspect, the upper and the lower members comprise atwo-part bodily movable armature, the members of which are separablewhen the current in the solenoids fails, and which furnish a completemagnetic circuit or field when the solenoids are energized. Thus,considering the two parts of the armature as complements ro f a whole, Ihave provided what I may term a :floating armature in which there is acomplete magnetic circuit. From another aspect, the lower member may beconsidered as the main armature, and the upper member as a supplementaland magneticfield-completing armature.

I may utilize the magnet which I have herein described for a variety ofpurposes which will be apparent to persons skilled in the art. Forexample, I may use it for opening or closing a circuit, which includesstationary spring contacts 2%, 24, mounted upon the base 14. The crossbar 17 of the -lower armature member is provided with a movable contact25, which, when the solenoids are excited, engages the spring con tacts24 to close the circuit therethrough. I may also use the lower member toaccomplishother work, by its acquired momentum after being released onfailure of current in the solenoids.

"As a matter of detail, the lower member may be guided in its movementsby a vertical diamagnetic pin 26 depending from the bracket 12 andpassing through an aperture in the cross bar 17. Stops 27 are alsolocated in the path of the lower armature to arrest its downwardmovement, as shown.

ICare should be taken in the construction of the two-part armature,comprising the two U-shaped opposing members, so to re'- late theirmasses that, when the alternating current of the desired maximumpotential is passing through the solenoid coils, the opposing forcesexeited upon said members will permit them to maintain a substantiallystabilized floating position in the magnetic field out of mechanicalcontact with any parts against which they might vibrate and produce ahum or chatter.

Having thus explained the nature of my said invention and described away of making and using the same, although without `attempting to setforth all of the forms in which it may be made or all of the modes ofits use, what I claim is 1. An 'alternating-current electromagnet,comprising a pair of solenoids, and an armature therefor consisting ofseparable oppositely arranged movable U-shaped meinbers which, when thesolenoids are energized, furnish a closed magnetic field, and aremechanically disconnected from all stationary portions of theelectromagnet.

2. An alternating-current electromagnet, comprising a pairof solenoids,and opposing movable armature members common to both solenoids -`butphysically disconnected therefrom, whereby, when the solenoids areenergized, the armature members float in the magnetic field.

3. An alternatingfcurrent electromagnet, comprising a lpair of uprightsolenoids, and opposing movableU-shaped armature meinbers common to andextending into the opposite endsof both said solenoids. Y

a. An alternatingcuirent electromagnet, comprising a pair of solenoids,and an unattached two-part armature commonfoboth solenoids, extendinginto both ends of tthe solenoids and furnishing a closed magneticcircuit and floating freely in the magnetic field of said solenoids`when the .latter are energized.

5. An alternating-current magnet, comprising a lpair of solenoids,.andan armature consisting `of normally-separated `opposing bodily-movablemembers arranged in .the magnetic field thereof, and each bodilymovabletoward `the other into contact therewith when the solenoids areenergized, thereby forming a closed magnetic circuit, said armature,when said solenoids are energized, freely floating in the magnetic fieldthereof, without `physical connection with any stationary part of themagnet.

6. An alternatingcurrent magnet, comprising a pair of solenoids, and anVarmature consisting of oppositely arranged bodily-movable f J-shapedmembers common to both solenoids and having plungers projecting intoopposite ends thereof.

'7. An yalternating-current magnet, comprising a pair of solenoids, andan armature consisting of oppositely ar 'anged bodily-movableU-shapedmembers common to both solenoids and havingfplungers projecting intoopposite ends thereof, said members being proportioned, as to magneticmass, .to cause one of said members to displace the other bodily whensaid solenoids are energized.

8. An alternating-current magnet, comprising a pair of solenoidsarranged in parallelism, and an armature consisting of a pair ofbodily-movable separable U-shaped members arranged to make contact witheach other between theends of the solenoids .to float freely in themagnetic field ofthe solenoids.

9. An alternating-current magnet, com-- prising a pair of solenoids andan armature common to both solenoids, floating in the magnetic fieldthereof and forming a closed supplemental movable armature above undmagnetic circuit.' Common to both solenoids and having plun- 10. Analternating-current magnet, comgers extending downwardly into said sole-10 prising a pair of vertical solenoids, a main noids.

arma-ture therefor common to both solenoids In testimony whereof I haveaflixed my and having plungers movable upwardly signature. y into saidsolenoids, and a bodily-movable GRANVILLE E. PALMER.

